Comparison between neonatal and adult carotid body responses to chronic intermittent hypoxia

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Previous studies from our laboratory have shown that chronic intermittent hypoxia (CIH) affects carotid body function in adult and in neonatal rats. In the present study we examined whether the carotid body responses to CIH are the same or differ between the neonatal and adult rats. Sensory activity was recorded from ex vivo carotid bodies harvested from neonatal and adult rats exposed either to CIH or to normoxia. Following CIH, carotid body responses to graded acute hypoxia were augmented in both neonatal and adult carotid bodies compared to corresponding controls. The onset of the augmented hypoxic sensitivity, however, occurred sooner (16h) in neonatal compared to adult carotid bodies (24h). Acute IH resulted in sensory long-term facilitation (LTF; i.e., long-lasting activation of baseline sensory activity) in adult CIH carotid bodies, whereas sensory LTF was effectively absent in neonatal CIH carotid bodies. The effects of CIH on carotid body were reversible after placing CIH animals in normoxic environment for 10d in adult carotid bodies. In sharp contrast, the effects of neonatal CIH persisted even in the adult life (2months). These observations demonstrate striking differences in the carotid body responses to CIH between neonatal and adult carotid bodies. Supported by NIH-HL-25830, and HL-76537.